Throttle body and method of assembly

ABSTRACT

A throttle body for an automobile includes a throttle shaft defining a rotational axis. The throttle shaft includes deformable members integrally formed about an exterior surface of the throttle shaft. A housing includes a bore. The throttle shaft extends through the bore with the deformable member partially-located within the bore. A bearing includes an inner surface and an outer surface. The bearing inner surface forms a press-fit connection with the deformable members to substantially prevent movement between the throttle shaft and the bearing in a direction parallel to the rotational axis.

CROSS-REFERENCE TO RELATED APPLICATIONS

The application is a continuation-in-part of U.S. application Ser. No.10/898,493, filed Jul. 22, 2004.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

REFERENCE TO A SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTINGCOMPACT DISC APPENDIX

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention generally relates to an air intake control device. Morespecifically, the invention relates to a throttle body and a method ofassembling a throttle body.

2. Description of the Related Art

Throttle bodies regulate the airflow to an internal combustion engine.In order to run properly, internal combustion engines require a precisemixture of air and gasoline and, therefore, throttle bodies are designedto adjustably control the airflow into the cylinders of the engine. Inorder to control the airflow that reaches the cylinders, the throttlebody includes at least one throttle plate attached to a throttle shaftsuch that the throttle plate is located within a throttle bore, orproximal to an end of the throttle bore. With rotation of the shaft, thethrottle plate is able to selectively obstruct airflow through thethrottle bore. More specifically, the throttle plate is able to rotatewith respect to the bore in order to adjust the cross-sectional area ofthe bore that is not obstructed by the plates (the “effective area”),thus controlling the amount of airflow that is permitted to flow throughthe throttle bore.

In order to effectively control the effective area, the throttle plateis sized and shaped to approximate the cross-sectional area of the boresso as to substantially or completely obstruct the bore when the throttleplate is perpendicular to the airflow (the “closed position”).Additionally, the throttle plate has a minimal thickness in order tosubstantially not obstruct the throttle bore when the plate is angledsuch that a throttle plate is not substantially perpendicular to theairflow (the “open position”).

During operation, if the engine is idling, only a little air is neededto mix with the small amount of fuel being injected into the engine.When the engine is idling, the throttle plate is therefore in the closedposition. Conversely, if the engine is operating at a speed higher than!idle, then more air is needed to mix with the increased amount of fuelbeing provided to the engine. At speeds higher than idle, the throttleplate is therefore in an open position of a varying angle with respectto the airflow, the angle varying within the air requirements.

In order to completely or substantially obstruct the bore when thethrottle plate is the dosed position, it is desirable for the throttleplate to be precisely sized and accurately located within the bore.

Furthermore, it is desirable for the throttle plate to be secured in thedirection parallel to the rotational axis of the throttle shaft(referred to as the longitudinal direction). This minimizes or preventsunwanted contact between the throttle plate and the bore inner surface.Contact between the throttle plate and the bore inner surface mayprevent the throttle plate from fully closing. Furthermore, contact maycause excessive friction between moving parts and premature partfailure. The control of the longitudinal movement of the throttle plateis hereinafter referred to as float control.

In order to improve float control, some currently-used throttle bodiesinclude a first press-fit connection between the throttle shaft and aninner race of a bearing, and a second press-fit connection between theouter race of the bearing, and the throttle body housing. However, thefirst press-fit connection may deform the throttle shaft during periodsof assembly or maintenance of the throttle body. Throttle shaftdeformation is undesirable because it may prevent the throttle shaftfrom being reusable after assembly or maintenance, thus potentiallyincreasing assembly and/or service costs.

Another float control method includes an assembly for longitudinallytrapping the inner race of the bearing in a predetermined position onthe throttle shaft. More specifically, the inner race is sandwichedbetween a first structure, such as a threaded nut, on a firstlongitudinal side of the bearing and a second structure, such as astepped-diameter of the throttle shaft, on a second longitudinal side ofthe bearing. However, this type of float control construction mayrequire complicated machining operations and part requirements.

Yet another float control method includes an clip located in a groovefor longitudinally trapping the inner race of the bearing in apredetermined position on the throttle shaft. More specifically, theclip is seated in a groove such as to contact the bearing on a firstlongitudinal side and such that the second longitudinal side of thebearing contacts the housing. However, this type of float controlconstruction may require complicated machining operations and may resultin undesirable, high-frictional contacts between the respectivestructures and the bearing.

Therefore, it is desirous to minimize both the longitudinal movement ofthe throttle shaft and the friction between moving parts, all whilereducing the manufacturing and assembly costs and complexities of thethrottle body.

BRIEF SUMMARY OF THE INVENTION

In overcoming the disadvantages and drawbacks of the known technology,the current invention provides a throttle body for an automobile and amethod of assembly of a throttle body. The throttle body includes athrottle shaft defining a rotational axis, a housing having a bore, adeformable member located on the throttle shaft and at leastpartially-located within the bore, and a bearing having an inner surfaceand an outer surface. The bearing inner surface forms a press-fitconnection with the deformable member to substantially prevent movement,in a direction parallel to the rotational axis, between the throttleshaft and the bearing.

In one aspect of the present invention, a throttle body for anautomobile includes a throttle shaft defining a rotational axis. Thethrottle shaft includes deformable members integrally formed about anexterior surface of the throttle shaft. A housing includes a bore. Thethrottle shaft extends through the bore with the deformable memberpartially-located within the bore. A bearing includes an inner surfaceand an outer surface. The bearing inner surface forms a press-fitconnection with the deformable members to substantially prevent movementbetween the throttle shaft and the bearing in a direction parallel tothe rotational axis.

In yet another aspect of the present invention, a method of assembly ofa throttle body is also provided by the present invention. The method ofassembly of a throttle body for an automobile includes providing atubular member defining a rotational axis. Forming deformable members onthe tubular member for forming a throttle shaft. Providing a housinghaving a bore. Extending at least a portion of the throttle shaftthrough the bore of the housing. Providing a bearing having an innersurface and an outer surface. Coupling the bearing inner surface withthe deformable members to form a press-fit connection and tosubstantially prevent movement between the throttle shaft and thebearing in a direction parallel to the rotational axis.

In yet another aspect of the present invention, a method is provided forforming a throttle shaft for a throttle body of an automobile. Themethod includes providing a tubular member that defines a rotationalaxis. Providing a forming tool having a split die having a plurality ofcontact points and uncompressed regions. Inserting the tubular member inthe forming tool. Compressing the forming tool against the tubularmember for displacing material to the uncompressed regions for forming aplurality of protruding splines.

Various objects and advantages of this invention will become apparent tothose skilled in the art from the following detailed description of thepreferred embodiment, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a throttle body embodying the principles of the presentinvention, including a throttle shaft and a pair of, bearings receivedwithin a housing, and a deformable member coupled with the throttleshaft and one of the bearings according to the first preferredembodiment of the present invention.

FIG. 2 is an enlarged view of the portion of the throttle body of FIG. 1encircled by line 2-2.

FIG. 3 a is a side view of the deformable member of FIG. 1 according tothe first preferred embodiment of the present invention.

FIG. 3 b is an axial view of the deformable member of FIG. 3 a.

FIG. 4 is a partial view of the deformable member on the throttle shaftaccording to the first preferred embodiment of the present invention.

FIG. 5 is a throttle shaft and a deformable member of a second preferredembodiment of the present invention.

FIG. 6 is a throttle shaft and a deformable member of a third preferredembodiment of the present invention.

FIG. 7 a is an axial view of a throttle shaft according to a fourthpreferred embodiment of the present invention.

FIG. 7 b is a side view of a throttle shaft according to the fourthpreferred embodiment of the present invention.

FIG. 8 is a partial cross-section view of the throttle shaft and bearingaccording to the fourth preferred embodiment of the present invention.

FIG. 9 is perspective view of a tool used to form the splines of thethrottle shaft according the fourth preferred embodiment of the presentinvention.

FIG. 10 is a method for forming the splines of the throttle shaftaccording to the fourth preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the present invention, FIG. 1 shows a throttle body 10used to control the airflow into the combustion cylinders of an internalcombustion engine of a motor vehicle. The throttle body 10 includes athrottle shaft 12 connected to a throttle plate 14 by an appropriatemeans, such as threaded fasteners or rivets 15. The throttle shaft 12and plate 14 are rotatably received within a housing 16 such that thethrottle plate 14 is positioned within a bore 20 receiving the airflow18. The throttle shaft 12 itself is extended between a pair of bores 24formed in opposite sides of the airflow bore 20.

During operation of the throttle body 10, the airflow 18 enters the bore20 which is partially or fully obstructed by the throttle plate 14and/or throttle shaft 12. More specifically, the throttle plate 14preferably has a size and shape placing its perimeter in close fitwithin that of the bore 20 in order to completely block the airflow 18when the throttle plate 18 is in a closed position (where the axialfaces of the throttle plate 14 are generally perpendicular to theairflow 18 through the bore 20, as shown in FIG. 1). As the throttleplate 14 is rotated with respect to the housing 16, openings (not shown)are formed between the perimeter of the throttle plate 14 and the bore20, which permit the airflow 18 to flow past the throttle plate 14 andinto the cylinders of the internal combustion engine. The amount of theairflow 18 that is permitted to flow past the throttle plate 14increases as the throttle plate is rotated towards an open position(where the axial faces of the throttle plate 14 are not perpendicular tothe airflow 18 and more and more closer to parallel within the airflow18).

The throttle shaft 12 is rotatably received by the bores 24 of thehousing 16. More specifically, a pair of bearings 26, 28 preferablyreceive the throttle shaft 12 on opposite sides of the housing 16 inorder to permit the throttle shaft 12 to rotate about a rotational axis30 defined longitudinally therethrough. The rotation of the throttleshaft 12 is preferably controlled by an automated mechanism, such as anactuator driving a drive gear 32 connected to the housing 16 and adriven gear connected or mounted to the throttle shaft 12.

Referring now to FIG. 2, the throttle shaft 12 preferably extendsthrough a first portion 24 a of the bore 24 such that a clearance 38 ispresent between the bore first portion 24 a and the throttle shaft 12.The clearance 38 is preferably of any appropriate size in order tosubstantially reduce or eliminate frictional contact between the shaft12 and the bore 24. In order to permit rotational movement between thethrottle shaft 12 and the housing 16, the bearing 26 preferably includesan inner race 40 coupled with the throttle shaft 12 and an outer race 42coupled with the housing 16. The inner race 40 and the outer race 42 arepreferably separated by low-friction rolling members, such as the ballbearings 44 shown in FIG. 2.

As discussed above, it is desirable to prevent longitudinal movement ofthe throttle shaft 12 (where longitudinal motion is defined as beinggenerally parallel to the rotational axis 30 shown in FIG. 1).Therefore, an end float control mechanism is preferably provided. FIG. 2shows a close-up view of one embodiment of a deformable member 36utilized in the present invention for float control that is coupled withthe bearing 26 and the shaft 12. The deformable member 36 shown in FIG.2 is referred to as a crush ring 36 and has a generally-circular ringshape, but other configurations may be used.

As discussed above, it is undesirable if deformation to the throttleshaft 12 occurs during assembly and maintenance of the throttle body 10.Therefore, in the present invention the inner race 40 is coupled to thethrottle shaft 12 via the crush ring 36. More specifically, the crushring 36 is located between the throttle shaft 12 and an inner surface 44of the inner race 40 in order to form a press-fit connection. Thepress-fit connection between the crush ring 36, the throttle shaft 12,and the bearing 26 is strong enough to substantially prevent movementbetween the throttle shaft 12 and the bearing 26 in the longitudinaldirection. More specifically, the crush ring 36 is plastically deformedby the press-fit connection between the bearing inner race 40 and thethrottle shaft 12.

In order to substantially prevent contact between the inner race 40 ofthe bearing 26 and the throttle shaft 12, a clearance 46 exists betweenthe inner race 40 and the throttle shaft 12. The clearance 46 is anyamount sufficient to prevent contact between the inner face 40 and, thethrottle shaft 12.

The throttle shaft 12 preferably includes a portion having a reduceddiameter, such as the groove 48 shown in FIG. 2. The crush ring 36 islocated within the groove 48 in order to properly position the crushring 36 on the throttle shaft 12 with respect to the bearing 26 duringassembly and maintenance of the throttle body 10. The groove 48 in FIG.2 has a shape such as to matingly receive the crush ring 36.

The outer race 42 preferably forms a press-fit connection with a secondsurface 24 b of the bore 24 in order to substantially preventlongitudinal movement between the outer race 42 and the housing 16.

Referring now to FIGS. 3 a and 3 b, in one configuration the crush ring36 is a generally-circular ring that substantially encircles thethrottle shaft 12. In order for the crush ring 36 to effectivelyplastically deform when forming a press-fit connection with the throttleshaft 12 and the bearing inner race 40, the material of the crush ring36 is preferably a relatively soft metal such as aluminum, but anyappropriate material may be used.

The configuration shown in FIGS. 3 a and 3 b includes a tapered endportion 50, having a tapered portion diameter 52, and a straight portion54, having a straight portion diameter 56. The tapered portion 50preferably extends across a length L₁ parallel to the rotational axis 30at an angle ρ with respect to a line parallel with the rotational axis30. The tapered portion diameter 52 varies across the length L₁ of thetapered portion 50, while the straight portion diameter 56 issubstantially constant. The length L₁ of the tapered portion 50 isapproximately one-third of the total length L₂ of the crush ring 36, butany appropriate length may be used. The angle φ of the tapered portion50 is preferably within a range of 5°-45°, but again, any appropriateangle may be used. In order to improve the method of assembly of thethrottle body 10, the tapered portion 50 is located adjacent to a leadend of the crush ring 36, as will be discussed in further detail below.

The crush ring 36 includes a slot 58 extending through the crush ring 36such that the respective diameters 52, 56 of the crush ring 36 arevariable. The variable diameters 52, 56 allow the crush ring 36 to beexpanded during installation onto the shaft 12 and deform uponpress-fitting of the bearing 26, as will be discussed in further detailbelow. In order to minimize high-pressure contact points between thebearing inner race 40 and the crush ring 36, the slot 58 preferablyextends along the length L of the crush ring 36 at an anglesubstantially oblique to the rotational axis 30. More preferably, theslot 58 forms an angle θ of 15°-60° with the rotational axis 30. Evenmore preferably, the slot forms an angle θ of approximately 30° with therotational axis 30. As shown in FIG. 3 b, the crush ring 36 in theundeformed state includes a minimum thickness 60 in the tapered portion50 and a maximum thickness 62 in the straight portion 54.

Referring now to FIG. 4, the details of a method of assembly of athrottle body embodying principles of the present invention will now bediscussed. The crush ring 36 is located in the groove 48 of the throttleshaft 12 such as to extend substantially around the throttle shaft 12.In one configuration, the crush ring 36 is located around the shaft byexpanding the diameter of a pre-formed crush ring until the slot fitsover the throttle shaft 12. In another configuration, a generally flatblank of material is wrapped around the groove of the shaft in order toform a substantially continuous ring. In yet another configuration, thecrush ring is a continuous ring that is formed, such as by a moldingprocess, while the blank material is around the throttle shaft. Inanother configuration, the crush ring is a preformed continuous crushring that is moved down the length of the throttle shaft into a desiredposition, such as into a groove in the throttle shaft. In thisconfiguration, the diameter of the pre-formed continuous crush ring maybe reduced once the crush ring is in the desired position.

After the crush ring 36 has been inserted into the groove 48 and beforeit has been deformed, the crush ring 36 preferably has a space to expandin the longitudinal direction as it contracts in the radial direction.More specifically, at least one gap 64 is formed between the crush ring36, a longitudinal end 66 of the crush ring 36, and a respective sidewall 68 of the groove 48. The crush ring 36 shown in FIG. 4 issubstantially centered within the groove 48 such that the gap 64 ispresent on each longitudinal end 66 of the crush ring 36.

Referring back to FIG. 2, once the crush ring 36 has been inserted intothe groove 48, the throttle shaft 12 is inserted into the bearing 26.During insertion of the throttle shaft 12 into the bearing 26, the crushring 36 is inserted into the bearing 26 forming a press-fit connectionand substantially preventing longitudinal movement between the throttleshaft 12 and the bearing 26 along the rotational axis 30. In order easethe insertion into the bearing 26, the crush ring 36 is preferablyinserted into the bearing 26 such that the tapered portion 50 is thelead portion of the crush ring 36 entering the bearing 26.

During insertion of the crush ring 36 and the throttle shaft 12 into thebearing 26, the crush ring 36 is radially compressed to a deformedthickness 72, which is less than the maximum thickness 62 of theundeformed crush ring 36. Depending on the amount of radial deformationthat the crush ring 36 undergoes, the tapered portion 50 may becompletely compressed such that the crush ring 36 has a substantiallyconstant thickness. Alternatively, a portion of the tapered portion 50remains undeformed and tapered after insertion into the bearing 26, asshown in FIG. 2. The crush ring 36 preferably expands in thelongitudinal direction such as to engage the side walls 68 of the groove48. The engagement between the crush ring 36 and the groove 48substantially prevents movement between the throttle shaft 12, the crushring 36, and the bearing 26.

As discussed above, the clearance 46 between the throttle shaft 12 andthe bearing inner race 40 substantially prevents deformation of thethrottle shaft 12 during insertion of the crush ring 36 into the bearing26. Furthermore, the deformation of the crush ring 36 is preferably aplastic deformation in order to form a more effective press-fitconnection.

Also during insertion of the crush ring 36 and the throttle shaft 12, apress-fit connection is formed between the outer race 42 of the bearing26 and the housing 16. The outer race 42 and the housing 16 alsopreferably form a substantially fluid-tight connection to prevent theairflow 18 from entering the bore 21 formed by the first surface 20 ofthe housing 16. Similarly, the bearing inner and outer races 40, 42 andthe ball bearings 44 also preferably form a substantially fluid-tightconnection.

Referring now to FIG. 5, an alternative configuration of a throttle bodyembodying the principles of the present invention will now be discussed.The throttle shaft 112 shown in FIG. 5 includes a groove 148 having avarying depth. More specifically, the groove 148 includes a taperedportion 148 a having a varying groove depth 74 and a straight portion148 b having a constant groove depth 76. The tapered portion 148 apreferably has a length of approximately one third of the length of thegroove 148. Additionally, the tapered portion 148 extends along itslength at an angle of 5°-45°, but any appropriate angle may be used. Inorder to improve the method of assembly of the throttle body, thetapered portion 148 a is preferably located adjacent to an end of thegroove 148.

The deformable member 136 in this configuration is preferably a crushring 136 having a substantially constant thickness across its length.More specifically, the first longitudinal end 166 a of the crush ring136 has a thickness 162 a and the second longitudinal end 166 b of thecrush ring 136 has a thickness that is substantially equal to thethickness 162 a. As a result of the substantially constant thickness anda generally flush connection between the crush ring 136 and the throttleshaft 112, the crush ring 136 effectively has a tapered portion 136 acorresponding to the groove tapered portion 148 a and a straight portion136 b corresponding to the groove straight portion 148 b. The crush ringtapered portion 136 a eases insertion of the crush ring 136 into thebearing 26, similarly to that discussed above with anotherconfiguration.

Referring now to FIG. 6, yet another alternative configuration of athrottle body embodying the principles of the present invention will nowbe discussed. The throttle shaft 212 shown in FIG. 6 includes a groove248 having a groove width 248 a and a groove depth 248 b. Furthermore, adeformable member 236 is referred to as a crush ring 236 located withinthe groove 248. The crush ring 236 has a generally circularcross-section, but other configurations may be used. A portion 236 a ofthe crush ring 236 is located within the groove 248 and a portion 236 bof the crush ring 236 extends outside of the groove 248 in order to bedeformed by the press-fit connection with the bearing during assembly.

The diameter of the crush ring 236 is preferably substantially equal tothe groove width 248 a such that the crush ring 236 is substantiallysecured within the groove 248 during assembly. Furthermore, the groove248 preferably has generally squared corners such that gaps existbetween the respective groove corners and the crush ring 236. Thus, thecrush ring 236 is able to expand into the gaps during deformation. Dueto the groove width 248 a being substantially equal to the diameter ofthe crush ring 236, the groove depth 248 b is preferably smaller thanthe groove width 248 a such that the portion 236 b extends outside ofthe groove 248.

The crush ring 236 is preferably comprised of a wire, such as analuminum wire. Similar to the tapered section discussed above, thearcuate shape of the portion 236 b of the crush ring 236 extendingoutside of the groove 248 eases insertion of the crush ring 236 into thebearing.

Alternative configurations of the throttle body discussed above may beused with the present invention. For example, the deformable member maycomprise a plurality of components located at various points around thethrottle shaft.

FIGS. 7 a and 7 b illustrate a throttle shaft according to a fourthpreferred embodiment. The throttle shaft 240, shown in FIGS. 7 a and 7b, includes an elongated tubular member 242 having a plurality ofprotruding splines 244 that are integrally formed with the elongatedtubular member 242. The protruding splines 244 extend axially along theexterior surface of the elongated tubular member 242 and aresubstantially parallel to one another. In addition, the protrudingsplines 244 also extend radially outward from the elongated tubularmember 242. Preferably, there are 4-12 protruding splines formed aboutthe circumference of the throttle shaft 240; however, more or lesssplines may be used depending on the diameter of the throttle shaft 240.

Since the protruding splines 244 are integral to the tubular member 242,the protruding splines 244 are formed from a same material as thetubular member 242 (i.e., such as steel). As a result, the protrudingsplines 244 include both elastic deformation properties and plasticdeformation properties. Each of the protruding splines 244 include abase section 246 that tapers as it extends radially outward to a topsection 248.

FIG. 8 illustrates throttle shaft 240 extending through the firstportion 24 a of the bore 24. Similar to FIG. 7 b, a clearance 38 ispresent between the bore first portion 24 a and the throttle shaft 240.The clearance 38 is of the appropriate size in order to substantiallyreduce or eliminate frictional contact between the throttle shaft 240and the bore 24.

The inner race 40 of the bearing 26 is coupled to the throttle shaft 240via the protruding splines 244 which are integrally formed on thethrottle shaft 240. The protruding splines 244 extend axially along thethrottle shaft 240 for a distance that is at least equal to a width ofthe inner race 40 of the bearing 26. The press-fit connection betweenthe protruding splines 244 of the throttle shaft 240 and the bearing 26is strong enough to substantially prevent movement between the throttleshaft 240 and the bearing 26 in the longitudinal direction. Morespecifically, the protruding splines 244 are both plastically deformedand elastically deformed by the press-fit connection between the bearinginner race 40 and the throttle shaft 240. That is, a substantial portionof the base section 246 is elastically deformed while a substantialportion of the top section 248 is plastically deformed. The combineddeformation properties of the base section 246 and the top section 248are strong enough to cooperatively retain the throttle shaft 240 to thebearing 26.

The elastic deformation properties of the bottom section 246 allow thethrottle shaft 240 to be removed from the bearing 26 (e.g., for service)and to be re-inserted while retaining an adequate press-fit retentionforce to maintain the coupling between the throttle shaft 240 and thebearing 26. Furthermore, as the protruding splines 244 are deformed, thetop section 248 of each respective spline deforms circumferentially asopposed to axially so that substantially no deformed material from theprotruding splines 244 displaces into the clearance 38.

The protruding splines 244 of the throttle shaft 240 are formed justprior to inserting the throttle shaft 240 into the bearing 26. Prior tothe formation of the protruding splines 244, the tubular member 242includes an exterior surface having a uniform diameter, as shown at 249in FIG. 7 a. After the protruding splines 244 are formed, the exteriorsurface of the tubular member 242 includes a roughly formed exteriorsurface in which the diameter may be non-uniform, as shown at 250 inFIG. 7 a, as a result of the forming operation.

FIG. 9 illustrates a forming tool 252 used to form the protrudingsplines 244 of the throttle shaft 240. The forming tool 252 includes asplit die having a first die half 254 and a second die half 256. Thefirst die half 254 and the second die half 256 each include a pluralityof contact points 258 which are used to swage or cold form the exteriorsurface of the tubular member 242. The first die half 254 and the seconddie half 256 are brought into contact with the tubular member 242 forcompressing the shaft from two sides. The plurality of contact points258 compress the exterior surface of the tubular member 242 therebydecreasing the diameter of the tubular member 242. Uncompressed regions260 between the plurality of contact points 258 receive displacedmaterial from the tubular shaft 242 as a result of the compression forceexerted thereon. The displaced material of the tubular member 242 isforced circumferentially to the uncompressed regions 260 adjacent theplurality of contact points 258. As the displaced material is forced tothe uncompressed regions 260, the displaced material extends radiallyoutward from the exterior surface of the tubular member 242 therebyforming the plurality of protruding members 244. The displaced materialis substantially unrestricted, with the exception of a respective wallsurfaces of the contact points of the forming tool, as it flows into theuncompressed regions 260, and as a result, the height and width of eachof the plurality of protruding members 244 may vary. Furthermore, theforming tool 252 may include hard stops to limit the amount of travel ofa respective die half and the amount of compression force exerted on thetubular member 242.

As shown in FIG. 7 a, the diameter of the exterior surface, showngenerally at 250, decreases as a result of the compression applied bythe forming tool 252. The compressed exterior surface 250 may include anuneven surface as a result of the roughly forced compression operation.However, the uneven compressed exterior surface of the tubular member242 does not factor into the press-fit operation since the throttleshaft 240 utilizes only the protruding splines 244 as a mating surfacefor the interference fit with the inner race of the bearing 26 shown inFIG. 9.

After the protruding splines 244 are formed, the throttle shaft 240 ispress-fit into each respective bearing. The forming operation of theprotruding splines 244 is performed immediately before the throttleshaft 240 is assembled into each respective bearing. As a result, theinsertion force required to press-fit the throttle shaft 240 into therespective bearing is utilized as a control parameter for forming theprotruding splines 244. That is, if a respective throttle shaft havingprotruding splines are identical (i.e., having equal dimensions), a samepredetermined force could be used to press-fit each respective throttleshaft in the respective bearings. Typically, sub-components are formedin mass batches and are then supplied to an assembly operation to beassembled in a respective component. Since forming tools typically havegradual wear rates as components are produced, SPC measurement data iscollected on the mass production parts at predetermined time or countintervals for verifying that the dimensional characteristics are withintheir respective tolerances (e.g., height and width, taper).

In the preferred embodiment, dimensional data on the protruding splines244 is not measured and collected. Rather, the adjustments to theforming tool 252 are gauged on the force required to insert the throttleshaft 240 into the respective bearings at the preceding assemblyoperation. Based on the force required to press-fit the throttle shaft240 into the bearing 26, required adjustments may be immediately made tothe forming tool at the previous operation. For example, as the formingtool wears, a same applied compression force exerted by the forming toolon the tubular member to form the protruding splines would result inless material being forced to the uncompressed regions, which in turn,results in a decrease in the height of the protruding splines. Adecrease in the height of the protruding splines 244 results in a lowerpress-in force required to insert a respective throttle shaft into arespective bearing since there is less material to deform whenpress-fitting the respective throttle shaft into the respective bearing.The force required to insert the throttle shaft 240 is directly relatedto the height and width of the protruding splines 244. If the forcerequired to the insert the throttle shaft decreases, then the height andwidth of the protruding splines 244 have decreased. Adjustments may bemade to the forming tool 252 to increase the compression force exertedon the exterior surface of the throttle shaft 240 for displacingadditional material into the uncompressed regions 260 which willincrease the height of the protruding splines 244. Since the protrudingsplines 244 for a respective throttle shaft is formed immediatelypreceding the assembly of the respective throttle shaft into therespective bearings, direct feedback of the insertion force is used tomonitor the formation of the protruding splines 244 without having tomeasure the height and width of each protruding spline for maintainingdesign tolerances. The protruding splines 244 may be roughly andnon-uniformly formed and adjustments may be directly made to the formingtool 252 for producing the protruding splines 244 based on the requiredforce to insert the throttle shaft 240 into the bearing 26. This reducesscrap and manufacturing cost as a result of not having to maintain tightdesign tolerances or producing stockpiles of formed throttle shafts thatare later determined to be out of specification.

FIG. 10 illustrates a method for forming the protruding splines on thethrottle shaft. In step 270, the tubular member is placed in the formingtool. In step 271, the tubular member is located axially and radially byhard points. In step 272, the forming tool is brought into contact withthe tubular member. In step 273, a compression force is exerted on thetubular member by the contact points of the forming tool. Material fromthe tubular member is displaced adjacent to the uncompressed regionsadjacent contact points of the forming tool for forming the plurality ofsplines as a result of the compression force exerted by the contactpoints. In step 274, hard stops limit the travel distance of the formingtool. This in turn limits the amount of compression exerted on thetubular member, and hence, overall height of the plurality of splines.

It is therefore intended that the foregoing detailed description beregarded as illustrative rather than limiting, and that it be understoodthat it is the following claims, including all equivalents, that areintended to define the spirit and scope of this invention.

1. A throttle body for an automobile comprising: a throttle shaftdefining a rotational axis, said throttle shaft including deformablemembers integrally formed about an exterior surface of said throttleshaft; a housing having a bore, said throttle shaft extending throughsaid bore with said deformable member partially-located within saidbore; and a bearing having an inner surface and an outer surface, saidbearing inner surface forming a press-fit connection with saiddeformable members to substantially prevent movement between saidthrottle shaft and said bearing in a direction parallel to saidrotational axis.
 2. The throttle body of claim 1 wherein said deformablemembers includes a plurality of protrusion splines extend axially alongsaid exterior surface of said throttle shaft.
 3. The throttle body ofclaim 2 wherein said plurality of protrusion splines extend radiallyoutward above said exterior surface.
 4. The throttle body of claim 2wherein said plurality of protrusion splines radially extend at varyingheights above said exterior surface.
 5. The throttle body of claim 2wherein said plurality of protrusion splines include elastic deformationproperties.
 6. The throttle body of claim 2 wherein said a top portionof said plurality of protrusion splines include plastic deformationproperties.
 7. The throttle body of claim 2 wherein said plurality ofprotrusion splines extend axially along said throttle shaft for apredetermined distance that is at least equal to an axial length of saidbearing.
 8. The throttle body of claim 1 wherein said deformable membersare substantially disposed under said bearing inner surface.
 9. Thethrottle body of claim 1 wherein said shaft is re-insertable within saidbearing while maintaining a substantially same press-fit retentionforce.
 10. A throttle body as in claim 1, wherein the throttle shaftcomprises a steel material.
 11. A method of forming a throttle shaft fora throttle body of an automobile, said method comprising the steps of:providing a tubular member defining a rotational axis; providing aforming tool having a split die having a plurality of contact points anduncompressed regions; inserting said tubular member in said formingtool; compressing said forming tool against said tubular member fordisplacing material to said uncompressed regions for forming a pluralityof protruding splines; press-fitting said tubular member into a bearingof said throttle body; measuring a press-fit force applied to saidtubular member for inserting said tubular member into said bearing;providing feedback indicative of said press-fit force applied to saidtubular member; and adjusting said compression force of said formingtool applied to said tubular member in response to said feedback. 12.The method of claim 11 wherein said forming tool forms said plurality ofsplines of at least a minimum axial length.
 13. The method of claim 11wherein said forming tool applies a predetermined compression force tosaid tubular member for forming said plurality of protruding splines.14. The method of claim 11 wherein said step of compressing said formingtool is restricted by hard stops mounted to said forming tool, said hardstops limiting a travel of said forming tool.
 15. A method of assemblyof a throttle body for an automobile comprising: providing a tubularmember defining a rotational axis; forming deformable members on saidtubular member for forming a throttle shaft; providing a housing havinga bore; extending at least a portion of the throttle shaft through saidbore of the housing; providing a bearing having an inner surface and anouter surface; and coupling the bearing inner surface with saiddeformable members to form a press-fit connection and to substantiallyprevent movement between the throttle shaft and said bearing in adirection parallel to the rotational axis.
 16. The method of assembly asin claim 15, further comprising the step of positioning said deformablemembers at least partially under said bearing inner surface.
 17. Themethod of assembly as in claim 16, further comprising the step ofplastically deforming a portion of the deformable members.
 18. Themethod of assembly as in claim 17, wherein said step of coupling saidbearing inner surface with said deformable members and the step ofplastically deforming a portion of the deformable member occursubstantially simultaneously.
 19. The method of assembly as in claim 18,wherein said throttle shaft remains substantially undeformed during saidassembly of said throttle body.
 20. The method of assembly as in claim15, wherein said step of forming said deformable members on said tubularmember is performed immediately preceding said step or extending saidthrottle shaft through said bore.
 21. The method of assembly of claim 20further comprising the step of monitoring an insertion force of saidcoupling of said throttle shaft to said bearing.
 22. The method ofassembly of claim 21 wherein said insertion force is provided asfeedback for adjusting a force required to couple said throttle shaft tosaid bearing.